1. Field of the Invention
The invention relates to a device for treating physiological conditions and more particularly relates to a device for treating diabetes or other physiological conditions through the use of a closed loop control device for sensing diabetic or other physiologic states and for delivering an appropriate amount of insulin or other appropriate medicament or drug, if required, from an implanted drug pump.
2. Description of Related Art
Diabetes is a disease where the body does not produce or properly use insulin, a hormone that is needed to convert carbohydrates such as sugar or starches into energy needed for daily life. It is not clear what causes diabetes, but both genetics and environmental factors such as obesity and lack of exercise seem to play roles.
There are two major types of diabetes: Insulin-Dependent (type I) and Non-Insulin-Dependent (type II). It is estimated that diabetes, in its various forms, affects 16 million people in the United States alone. In the United States, approximately 1,700 people are diagnosed with diabetes every day with about 625,000 people diagnosed in a year. Type II diabetes is the most common form of the disease accounting for about 90-95 percent of all diabetes cases. Type I diabetes accounts for 5-10 percent of all cases of diabetes.
Insulin-Dependent (type I) diabetes is an autoimmune disease where the body does not produce any insulin. This disease occurs most often in the first two decades of life but can develop up to about age 40. People with this type of diabetes must take daily insulin injections to stay alive.
Non-Insulin-Dependent (type II) diabetes is a metabolic disorder resulting from the body""s inability to make enough of or properly use insulin. Environmental factors such as obesity and lack of exercise appear to play a large role in this type of diabetes. Because many American adults are overweight and don""t exercise, type II diabetes is nearing epidemic proportions in the U.S. Non-Insulin Dependent diabetes usually gradually develops after about age 35.
Diabetes is the fourth-leading cause of death by disease in the United States. The American Diabetes Association estimates that more than 169,000 died from the disease and its related complications in 1997. Some of the complications associated with diabetes are blindness, kidney disease, nerve disease, amputations, heart disease and stroke.
Diabetes is the leading cause of new cases of blindness in people ages 20-74. Each year, it is estimated that from 12,000 to 24,000 people lose their sight because of diabetes. Ten to twenty-one percent of all people with diabetes develop kidney disease. In 1992, an estimated 19,800 people initiated treatment for end stage renal disease (kidney failure) because of diabetes.
In addition, about 60-70 percent of people with diabetes have mild to severe forms of diabetic nerve damage. In severe forms, this nerve damage can lead to lower limb amputations. Diabetes is the most frequent cause of non-traumatic lower limb amputations. The risk of a leg amputation due to nerve damage is 15-40 times greater for a person with diabetes than for a person without diabetes. Each year, an estimated 54,000 people lose their foot or leg to diabetes related amputations.
People with diabetes are two to four times more likely to have heart disease than those who don""t have diabetes. Heart disease is present in 75 percent of diabetes-related deaths. Annually, diabetes related heart disease is estimated to cause more than 77,000 deaths. Further, people with diabetes are two to four times more likely to suffer a stroke than people without diabetes.
The American Diabetes Association estimates diabetes to be one of the most costly health problems in America. Health care and related costs for treatment, as well as the opportunity costs of lost productivity are estimated to be nearly $92 billion annually.
U.S. Pat. No. 5,569,186, issued to Peter C. Lord and Fredric C. Coleman on Oct. 29, 1996, entitled xe2x80x9cClosed Loop Infusion Pump System with Removable Glucose Sensorxe2x80x9d discloses an infusion pump system having a removable in vivo glucose sensor and an implantable infusion pump. The glucose sensor determines the concentration of glucose in the user""s blood and then signals the implanted pump to deliver a selected amount of medication, such as insulin, to the user. Signaling is accomplished via a direct or telemetric connection between the sensor and the pump.
U.S. Pat. No. 5,279,543, issued to Glikfeld et al. on Jan. 18, 1994, discloses an iontopheretic device to determine the level of glucose in a user""s body combined with an insulin pump or iontopheretic delivery system and feedback to administer appropriate levels of a insulin to diabetic patients.
It has been a goal of those developing medical devices to treat diabetes to produce a fully implantable system that mimics the body""s own system for regulating glucose. Such a system would require a sensor to sense the level of glucose in the blood, a device to infuse insulin or similar hormone to control the level of glucose and means for relaying the results of the glucose sensed to the device to infuse insulin so that a closed loop is formed. In this way, the system would automatically react to different levels of glucose and provide an appropriate level of insulin.
Unfortunately, such a fully implantable system has not yet been created. Much work has been done to develop ChemFETs and other sensors that can detect the level of glucose in the blood. However, when implanted, these sensors only have a lifespan of a few days at best. To be practical, implantable sensors to detect the level of glucose in the blood need to have a lifespan of at least several months.
A device to determine the level of glucose in a patient""s body and provide a therapeutic amount of insulin or a similar drug is disclosed. The level of glucose in the patient""s body is determined by painlessly iontopheretically sampling the patient""s blood and then analyzing the resulting sample to determine the level of glucose. The information about the level of glucose is transmitted to an implanted drug pump in the patient""s body. In the preferred embodiment, the glucose sensor is an external sensor applied to the user""s skin. In an alternate embodiment, the sensor may be implanted. The preferred method of transmitting information about the level of glucose determined by the sensor is transmitted to an implanted drug pump in the patient""s body is via a so called xe2x80x9cbody busxe2x80x9d. The xe2x80x9cbody busxe2x80x9d is a telemetry system where the patient""s own body provides the interconnection between the iontopheretic device and the implanted drug pump.
It is therefore a primary object of the invention to provide a system that mimics the body""s own system for administering an appropriate dose of insulin.
It is another object of one embodiment of the invention to provide a system that mimics the body""s own system for administering an appropriate dose of insulin including an external sensor.
These and other objects of the invention will be clear from the description of the invention given herein and particularly with reference to the attached drawings and the Detailed Description of the Invention. Throughout this description, like reference numbers refer to like elements.